Yes you can have the same backup image duplicated (vault) couple times, if that's what you want.
The limitation is - how many backup pcopies are allowed in your environment? Check your setting of "Maximum backup copies" in Master server's Global Attributes properties. For example, if you only allow 2 copies maximum, you can only vault/duplicate a backup image once.
Also, you need to give the vault profile enough days to go back to find that "last weekly full" backup.